Pro Football Focus Stat Shows How 49ers Pass Defense Went From Worst to First

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Richard Sherman #25 of the San Francisco 49ers kneels after an injury to Ahkello Witherspoon #23 during their NFL game against the Seattle Seahawks at Levi's Stadium on December 16, 2018 in Santa Clara, California.

Amajor reason why the San Francisco 49ers opened the season with an eight-game win streak and ended it with a trip to the Super Bowl was due to the 49ers ability to cover.

Pro Football Focus recently tweeted out an eye-catching statistic centered around San Francisco’s “coverage grades,” a measure that the publication uses to rate individual defenders while in pass coverage.

If it isn’t clear, these numbers rank the 32 defenses from each of the 2019, 2018 and 2017 seasons in terms of coverage grades.

For the 49ers the change that is most interesting is the jump from having the worst grade of all three seasons for their 2018 season to having a top-10 defense over the past three years.

The jump doesn’t necessarily come as a surprise to some 49ers fans who have watched general manager John Lynch and head coach Kyle Shanahan build through the draft and free agency, but it was still a dramatic improvement in terms of how quickly San Francisco translated their additions to success.

What Happened?

The 2017 and 2018 seasons were tough ones for the 49ers, and were part of a four-year stretch in which the team didn’t find much success on the field.

San Francisco went 17-47 over that stretch, never winning more than six games in a season as the team transitioned from a squad that made three straight NFC Championship games and added a Super Bowl appearance to boot.

When the 49ers hired Shanahan as the replacement to Chip Kelly, the team brought in defensive coordinator Robert Saleh to revamp the San Francisco defense. While it didn’t immediately translate to success, the team began to build.

High-profile additions like defensive lineman DeForest Buckner and Arik Armstead became the basis for the defense, with players like safeties Jimmie Ward and Jaquiski Tartt began to find their role as two- and three-year veterans.

2018 saw the additions of linebacker Fred Warner through the draft and corner Richard Sherman through free agency. Interestingly enough, the 49ers defense actually regressed statistically, giving up more points and passing yards from 2017 to 2018.

The Breakthrough

The numbers may not have gotten better initially, and certain factors such as the loss of quarterback Jimmy Garoppolo for the 2018 season made things difficult for Saleh and his team.

However, from Week 1 of 2019, it was apparent that the 49ers’ defense was on another level, allowing just 10.6 points per game in the first six weeks of the season.

San Francisco’s defense didn’t slow down despite eventually having their opening eight-game winning streak ended, leading the NFL in passing yards allowed during the regular season, limiting opposing passing offenses to a staggering 169.2 passing yards per game.

Lynch recently opened up about the philosophy behind his team’s build on 49er Insider, NBC Sports’ Matt Maiocco’s podcast, saying that the defensive front is a key cog and that the secondary is a group they like a lot, although he’s willing to improve it when the time comes.

“We were the No. 1 pass defense in football,” Lynch said. “And I think a lot of people point to up front, and, yeah, that is our philosophy. We build up front. I know from playing that position, when those guys are humming up front, when they’re putting pressure on a quarterback, when they’re knocking him down, when they’re sacking him, it makes your job a lot easier.”

“We like [the secondary]. We like everything they bring. We understand we’re going to have to pay some attention to it moving forward.”

The addition of defensive end Nick Bosa and the dominance of the 49ers defensive front deserves a sizable amount of credit, but San Francisco’s linebackers and secondary embraced the defensive identity that Lynch mentioned: a ferocious, unrelenting pass-rushing front with an opportunistic group of linebackers and defensive backs.